> Van: James Cameron <quozl@US.NETREK.ORG>
> Aan: PICLIST@MITVMA.MIT.EDU
> Onderwerp: Re: Button Pressing Behavior
> Datum: dinsdag 11 mei 1999 0:37
>
> Wagner,
>
> I tried this on a recent Technical Aid to the Disabled project, but I
> had some problems with EMF noise triggering.  Even though there is a LED
> there to Vcc, the input line is effectively floating when not driven
> either way.  It can jump up to the trigger voltage of the PIC input
> before the LED activates and begins to draw current.

Yes, that was one of the things I found out some time ago too.  The reason
behind this is that a LED behaves as a sort of a Zener-diode.  When it's
off no electrical connection seems to exist between the two legs of the
LED.  So, you can't use a LED in a circuit that should function as a
Pull-up.  The way to go is to place a Pull-up (or down) resistor parallel
to the LED (& series resistor), as you did/found out.

Greetz,
  Rudy Wieser